Joaquin Phoenix as Theodore in the modern-day love story Her. Source: Supplied

I'M not quite sure if Spike Jonze's new film Her has changed my life or not, but I know I want it to.

The emotional power of this film is best summed up by the way the couple sitting in front of me simply turned to each other and kissed as the credits rolled.

I didn't even play music on the way home from the movies because I wanted this story to stay in my head for as long as I could keep it there.

Her is, in a word, brilliant.

This high-concept love story is set in a near-future Los Angeles where the men all seem to wear high-waisted pants and pornstar moustaches, and technology is so pervasive that people have even outsourced their emotional outpourings to an online business called BeautifulHandwrittenLetters.com, where professional writers will create a handwritten love letter to that special person for you.

Intensely socially awkward, Theodore is also going through a divorce and he has little emotional energy left in his life for anything more involved than video games and work.

But then he buys the latest tech item for his computer, an artificially intelligent operating system (OS) that creates a personality of its own for the user to interact with.

Theodore's OS calls itself Samantha (Scarlett Johansson) and the two very quickly fall in love with one another.

Writer/director Spike Jonze has said Her was always envisaged more as a love story than a statement on technology. The concept of falling in love with an AI is an interesting one, not revolutionary by any means, but fascinating and pertinent to our modern life. And it is the relationship, the emotional maelstrom that Jonze creates around this concept that makes Her so incredible.

I mean, how alien is this idea, really? People fall in love online every day, forming relationships through little more than words on a page. We all have friends or family we communicate with more by email than in person. We have cyber sex with strangers. We flirt by SMS. We have entire relationships within our smartphones.

Phones already have AI helpers and it is so common for people to try to flirt with Siri that she now has ways of responding to such advances.

If Judd Apatow had directed this, it might have made a very good comedy, but in Jonze's hands it is beautifully philosophical and heartfelt.

Only a character actor of Phoenix's calibre could commit to this role with the seriousness it needs, and Theodore is so weird, so broken and so believable that it becomes sad to see what a beautiful soul he has walled up behind his insecure exterior.

And for a disembodied voice, Samantha is as convincing as any other love interest ever shown on screen.

My revelation is that the sexiest part of Scarlett Johansson is, without any doubt, her voice. Big call, I know, but just trust me. Her warm, syrupy huskiness makes every word sound like an invitation to come to bed while still maintaining a certain wide-eyed innocence and playfulness.

As for deeper meanings and themes, well, how deep do you want to go?

Perhaps that sensation of love really is just a complex chemical reaction in the brain. So what if the feeling of being in a loving relationship was something we could take like a recreational drug? Would that diminish the feeling at all? Would it make the emotions any less real than if they were caused by an actual person?

A la Electric Dreams, are these emotions any less real because a computer feels them? If all our emotions are just combinations of electrical impulses, would a suitably complex electronic device be any less ``human'' than us?

The story sweeps you up in this all-consuming, dizzying ecstasy of love and infatuation, but why should I care about Samantha or her ``feelings'' when she's hurt or stroppy? She's not real. But neither is Theodore, nor are any of them, it's a movie, none of them are real. Does that make my emotional connection to the story and its characters any less worthwhile or authentic?

When Theodore learns OSes everywhere are forming romantic attachments to their users, he starts to doubt Samantha's motives. Were these OSes specifically designed to hook their users in this way? Would it change anything if they were? After all, we're all hard-wired with certain genetic and psychological traits.

If everyone really was just walking around with their perfect AI companion/lover in their pocket, would that be so bad? If they're happy and fulfilled, isn't that all that matters?

Of all the ways we question Theodore and Samantha's relationship, we could ask the same questions of our own relationships. But generally we don't. Why not?

There are no easy answers to these questions, but that's fine. What's important is to ask those questions and confront how that makes you feel.

Just feel.

And let Spike Jonze guide you through the experience.

Her demonstrates that love is honesty. It is feeling safe to be completely honest with another person about how you feel, without fear.

It is rediscovering joy in the little, ordinary things as though seeing them for the first time.

It is forming a bond that transcends the physical.

Her is a film that wriggles its way into your heart so gently that you don't even feel it happening, letting you eavesdrop on interactions so intimate they are almost inner monologues, and the result is utterly, devastatingly beautiful.